1. Field of the Invention
The present application relates to a technical field of a display apparatus, and more particularly to a liquid crystal lens and a liquid crystal display device.
2. Description of Related Art
A stereoscopic display device usually adopts a naked-eye three-dimensional display. The naked-eye three-dimensional display mainly installs a light splitting device such as a liquid crystal lens at a light-emitting side of a two-dimensional (2D) display panel to respectively transmit an image having a left-right parallax and displayed on the screen panel to a viewer's left eye and right eye. Through the mixing of the brain, the viewer can obtain a stereoscopic perception.
Wherein, the liquid crystal lens mainly adopts a transparent material to manufacture a rod-lens array with a certain size. Through refraction, the lights in different pixels of the display panel emit with different polarization directions in order to separate the image having the left-right parallax.
With reference to FIG. 1, FIG. 1 is a schematic diagram of a lens unit of a liquid crystal lens according to the prior art. As shown in FIG. 1a, when no voltage is applied on the liquid crystal lens, the deflection directions of the liquid crystal molecules corresponding to two adjacent and strip-shaped electrodes are the same. At this time, a center and an edge of the liquid crystal layer corresponding to the electrodes have no difference in the refractive index.
As shown in FIG. 1b, when a voltage is applied on each of the electrodes of the liquid crystal lens, the liquid crystal molecules generate deflections under the function of the electric field. The center and the edge of the liquid crystal layer corresponding to the electrodes generate a difference in the refractive index. In a focus mode, phases form a lens-like distribution. The viewer can obtain a 3D image having a left-right parallax. Wherein, different electrodes are applied with different voltages. The liquid crystal molecules corresponding to the electrode which a maximum voltage is applied on are straightest such that the equivalent refractive index neff is the smallest. Two electrodes which the maximum voltage is applied define an opening width value of one lens unit.
As shown in FIG. 2, L1 is a curve diagram of the equivalent refractive index corresponding to the lens unit of the liquid crystal lens in an ideal condition, and L2 is a curve diagram of the equivalent refractive index corresponding to the lens unit of the liquid crystal lens in an actual condition. Wherein, in the ideal condition, when the electrode is applied with a maximum voltage, the equivalent refractive index neff of the liquid crystal molecules is n0 (n0=1.55).
Because the liquid crystal molecules are affected by an alignment film and the liquid crystal molecules squeeze and push with each other at an edge of two lens units. As a result, when the maximum voltage is applied on the edge of the two adjacent lens units, the liquid crystal molecules corresponding to the strip-shaped electrode at the edge of the two adjacent lens units cannot be completely straight. The above situation cannot be improved even increasing the maximum voltage such that the actual neff is greater than n0. As a result, the three-dimensional (3D) crosstalk is generated and the 3D display effect is affected.